1. Field of the Invention
The present invention is directed to an improved brush device for an electrical machine.
2. Description of the Prior Art
A brush device of the type with which this invention is concerned has at least one brush and at least one element for pressing the brush against a preferably rotating contact element. As a rule, the pressing element is a helical spring or a scroll spring. The contact element can be a commutator or a slip ring. The pressing element should reposition the brush as it wears down and prevent it from lifting off, for example due the contact element being out of round. The more powerful the pressing element is designed to be, the less danger there is of a liftoff. But this also increases the wear. Finally, the necessary play in the guidance of the brush also permits the occurrence of undesirable vibrations due to fluctuations in the coefficient of friction.